Control system for fluid fuel burners of the hot wire ignition type



NOV. 29, 1932. E, MCCABE 1,889,447

CONTROL SYSTEM FOR FLUID FUEL BURNERS OF THE HOT WIRE IGNITION TYPE Filed Feb. 7, 1950 5 Sheets-Sheet 1 I INVENTOR IRA ELM CABE.

Nov. 29, 1932.

l. E. MOCABE 1,889,447

CONTROL SYSTEM FOR FLUID FUEL BURNERS OF THE HOT WIRE IGNITION TYPE Filed Feb. 7, 1930 3 Sheets-Sheet 2 ,7 O O 0 I rw I I INVENTOR IRA E. M CABE (d M A TORNEY Nqv. 29, 1932. l. E. Mcc 1,889,447

CONTROL SYSTEM FOR FLUID FUEL BURNERS OF THE HOT WIRE IGNITION TYPE ATTORN EY Patented Nov. 29, 1932 UNITED STATES IRA E. MOCABE, OF CHICAGO, ILLINOIS CONTROL SYSTEM FOR FLUID FUEL BURNERS OF THE HOT WIRE IGNITION TYPE Application filed February 7, 1930. Serial No. 426,520..

This invention relates to improvements in controls for electrically operated liquid fuel burners and, more particularly, to a control system for fluid fuel burners of the hot wire ignition type.

In liquid fuel burners of this type the fluid fuel discharged into the combustion chamber of the furnace or heater to which the burner is applied is ignited by a resistance wire in an electric circuit being brought into incandescence by the passage of an electric current therethrough. In the usual control system of an electrically operated and controlled fluid fuel burner, a room thermostat is customarily employed to close and open the control circuit to cause the burner mechanism to start and cease functioning. In the hot wire type of ignition it is, therefore, necessary to preheat or cause the ignition resistance wire to become incandescent before the fluid fuel is supplied to the combustion chamber, and to insure ignition of the fluid fuel the ignition wire when once brought to incandescence must be maintained incandescent throughout the enire period allowed for the ignition to occur. If the electric circuit containing the ignition resistance varies in voltage, the fluctuations may reduce the temperature produced in the ignition resistance to such an extent as to fail to ignite the fluid fuel. In electrically operated and controlled fluid fuel burners, it is customary to provide a safety device which will cause the burner mechanism to cease operating if ignition fails initially or if combustion fails after being initiated.

It is an object of this invention to provide a control system for fluid fuel burners of the hot wire ignition type which will provide a definite period for preheating or brmging the ignition resistance to incandescency for a predetermined time prior to the operation of the burner mechanism to supply fluid fuel to the combustion chamber and at the same time insure a uniform flow of current of constant intensity through the ignition circuit, and after the starting of the burner mechanism provide means which will break the control circuit a predetermined time thereafter if the fuel does not ignite initially or if combustion fails after initiation.

With these and other objects in view reference is made to the accompanying sheets of drawings, which illustrate an embodiment of this invention, with the understanding that minor detail changes may be made without departing from the scope thereof.

In the drawings:

Figure 1 is a wiring diagram illustrating an embodiment of this invention.

Figure 2 is an enlarged detail View in front elevation of the control panel which mounts certain devices diagrammatically illustrated in Figure 1.

Figure 3 is a fragmentary view partly in vertical central section and partly in side elevation of an application of this control system to a rotary type of fluid fuel burner, as installed in a domestic heater or furnace.

This invention relates to the same general subject matter as disclosed in my companion application executed of even date herewith Serial No. 426,521 filed February 7, 1930, and differs mainly in the manner in which the safety device which operates upon failure of combustion either initially or after establishment, is employed.

Figure 1 illustrates the incoming commercial current passing through a room thermoso stat R, of commercial construction thence through a boiler control B, of commercial construction, to the binding post 1 upon the control panel P and thence through a safety switch S to a binding post 2. Here the current branches, one portion of which passes to a mercury tube switch 3 and the other to the binding post 4 in a thermal switch TS or stack safety of commercial construction, preferably of the type illustrated in my prior ending application Serial No. 311,436,

led ct. 10, 1928. The room thermostat R and the boiler control B are both shown in closed positions. It is customary in fluid fuel burners to emplo both of these devices, the room thermostat being located in a portion of the building where a predetermined uniform temperature is desired, and will operate to closethe circuit when the temperature has descended below the desired degree. The

boiler control B is attached to the furnace or boiler'and normally remains closed, but will open whenever the conditions within the boiler approach the danger line. The ther- 5 mal safety TS includes two mercury tube switches 5 and 6 whichare so supported upon the operating mechanism that when one switch is open the other switch is closed, and when tilted to reverse the relations, the open 10 switch will be closed before the closed switch is opened, and vice 'versa. The switches in the thermal switch TS are shown in the positions assumed when the furnace is cold. The safety switch S is also of commercial construction and is preferably constructed and operated in the manner illustrated and described in my prior Patent No. 1,643,389 of November 8, 1927. As shown in Figure 1 the thermal switch 5 is normally closed, the

mercury tube switch 3 is tiltably mounted upon the upper side of a solenoid A which is of commercial construction and includes a dashpot D for retarding the movement of the solenoid core C, as shown in Figure 2. The

2 switch 3 is so mounted that when the solenoid is energized the upward movement of the core C will tilt the switch. Figure 1 illustrates the mercury tube switch 3 in open position, which is the position assumed when the solenoid is deenergized so that in this position no current passes from binding post 2 through switch 3.

The incoming current having been traced through bindin post 1, safety switch S, binding post 2 to binding post 4 in the thermal switch, and, as the switch tube 5 is shown in closed position, the current passes therethrough to the binding post 7, that is of the thermal switch TS, and thence 4 to the binding post 8 upon the panel P, from binding post 8 the current passes through the heating element 9 of the safety switch S to binding post 10 upon the panel to the windings of the solenoid A and from these windings tothe windings of the primary coil PC of the transformer T and thence through binding post 12 upon the panel, back to the commercial line. The transformer T is constructed as shown in my prior ending application Serial No. 331,542 filed anuary 10, 1929. The secondary coil SC of transformer T is connected in circuit with the resistance wires W, preferably of nickelchromium alloy wire, flattened and bent back upon themselves as shown in Figure 1 which will become incandescent upon continuous passage of the secondary circuit therethrou h so that when the fluid fuel was passe thereover, it becomes ignited.

From the diagrammatic illustration on Figure 1, it is seen that when the room thermostat R is closed the commercial circuit passes through the boiler control B, safety switch S, thermal switch 5, heating element 9 of the safety switch, solenoid and transformer T, as these elements are all connected in series. The solenoid A is so adjusted that it will not operate to tilt the mercury tube switch 3 to closed position until after the ignition wires W have become incandescent. The closing of the mercury tube switch 3 closes a circuit from binding post 2 through switch 3 to binding post 13. Here the circuit branches, a part of it passing through the electrically operated oil valve or fluid fuel valve V, which is of commercial construction and is interposed between the source of fluid fuel and the discharge thereof in the burner nozzle, through binding post 11 back to binding post 12 and then returning to the commercial line. The other portion passes through the motor M to binding post 12 and thence to the return line of the commercial circuit. U on. energizin the valve V and motor M, uid fuel will be supplied to the combustion chamber. If, for any reason, fuel so supplied at this time is not ignited the thermal switch TS remains in the positlon shown in Figure 1 and the continuing of the passage of the current through heating element 9 of the safety switch S actuates a thermal release mechanism and causes the safety switch to break the circuit therethrough whereupon the solenoid A, trans former T, valve V and motor M are immediately deenergized causing the burner mechanism to cease functionng and these parts cannot again function until the safety switch S is manually closed or reset.

If upon closing the circuit through the room thermostat, and combustion occurs in the normal functioning of the control system, the thermal switch TS, which is responsive to combustion conditions, will be actuated so that the switches 5 and 6 will be tilted and the switch 6 will close the circuit from binding post 4 to binding post 14 upon the thermal switch to binding 0st 13 and from thence through the valve and motor M to the return of the commercial line through binding post 12 as hereinbefore described. The operation of the thermal switch TS in closing the switch 6 thereafter opens the switch 5 so that during the normal operation the switch 5 breaks the circuit throu h the heating element 9, solenoidAandtrans ormer T, whereupon the solenoid A becomes deenergized allowing the switch 3 to assume the open position. When the 'room thermostat R opens normally, the circuit to the valve V and motor M is immediately broken and combustion ceases, whereupon thermal switch TS cools and assumes the position shown in Figure 1, so that when the room thermostat R normally closes, the elements of the control being in normal position, will again cause the normal functioning of the burner.

If, however, during the normal operation of the burner mechanism in producing heat, should combustion fail for any reason, such as a stoppage in the supply of fluid fuel, the thermal switch TS will cool causing the switch 6 to break the circuit to the fuel valve and motor and close switch 5 to close the circuit from the commercial line through the heating element 9, solenoid A and transformer T. After the cause of stoppage has been removed before the heating element 9 actuates the safety switch S, normal ignition will occur. However, if the fuel is not delivered within this time heating element 9 will actuate the safety switch S to break the circuit therethrough whereby all operation or future operation of the various elements cease and the system will not function again, nor can ignition occur until the safety switch S is manually reset.

What I claim is:

1. A control system for an electrically operated fluid fuel burner of the hot wire ignition type, including a source of commercial electricity having a safety switch therein; a preheating circuit having a normally closed thermal switch responsive to combustion to open, a safety switch actuator, a slow acting solenoid, and a transformer all connected in series to said safety switch; a hot wire igniter in the secondary circuit of said trans former; a starting circuit in parallel with said preheating circuit having therein in series a switch actuated to close by said solenoid and a burner motor; a means connected to said solenoid tocause its slow action and delay operation of its switch for a predetermined time; an additional normally open switch responsive to combustion to close before said first switch opens; and a running circuit in shunt around said solenoid actuated switch and having therein said normally open combustion responsive switch.

2. A control system for an electrically operated fluid fuel burner of the hot wire ignition type, including a source of commercial electricity having a safety switch therein; a preheating circuit having a normally closed thermal switch responsive to combustion to open, a safety switch actuator, a slow acting solenoid, and a transformer all connected in series to said safety switch; a hot wire igniter in the secondary circuit of said transformer; a starting circuit in parallel with said preheating circuit having therein in series a switch actuated to close by said solenoid and a burner motor; a means connected to said solenoid to cause its slow action and delay operation of its switch for a predetermined time; an additional normally open switch responsive to combustion to close before said first switch opens; and a running circuit in shunt around said safety switch actuator said solenoid actuated switch and said transformer and having therein said normally open combustion responsive switch.

IRA E MOCABE. 

